Ask Reef Builders #2: Why do you believe pH is so important?

Welcome to ‘Ask Reef Builders’, a column where we’ll take some of your best questions and share our responses from which all our readers can learn. For years we’ve answered questions fielded through twitter, facebook and youtube comments, and now we’re happy to help even more of our readers and viewers get the most from their reef tanks.

Reef Builders why do you believe ph is so important? There is a study showing ph is not so important to sps as people once thought.

This question was very interesting to me not just because of what it asked, but also how it was worded. The question did not simply ask “why is pH important” but why I believed it to be, as if this was a matter of opinion. For the sake of this discussion, chemistry is factual, absolute, and not really open to ‘interpretation’ or beliefs.

I like multiple devices to test and monitor pH (this pH of 7.86 is not ideal and was taken in the morning when pH is lowest, and before a KalkReactor was added to this system)

After temperature and salinity, pH is the most important parameter of water governing all chemical and biological reactions. As far as reef aquarists are concerned, a higher pH will lead to faster coral growth, faster coralline algae growth, and higher calcification rates of anything with a shell or skeleton – crustaceans, clams, tubeworms, everything!

This reefer’s doubts about pH stemmed from a study showing that a single coral species, Porites cylindrica had no significant deviation of internal pH relative to the external environment. Simply stated, this coral was able grow and calcify at a steady rate even in depressed pH.

First of all P. cylindrica is a super hardy coral that often lives in marginal environments with high turbidity and less than ideal conditions. This means it has adapted to hyper regulate its pH and this is also why this yellow finger is a hardy coral in aquariums.

What’s important to note is that ALL corals regulate their internal pH to a higher level to precipitate aragonite crystals of calcium carbonate. This pH regulation takes energy – you can’t get something for nothing – and the lower the pH the harder that coral will have to work to achieve a proper internal pH chemistry.

Porites cylindrica is a very hardy stony coral species and its ‘tolerances’ should not be broadly applied to all reef corals.

With temperature, salinity, chemistry and nutrients remaining the same, raising the pH level of aquarium water is the best thing you can do to make corals grow faster. In fact, you can add all the food, increase the light, raise the temperature, dose trace elements and amino acids but the pH of seawater is the limiting factor to coral growth.

Yes corals regulate their internal pH and this is how it grows, but the lower the pH, the more energy it will consume in the process and in higher pH, corals have a much easier time growing, and growing faster.

Jake Adams has been an avid marine aquarist since the mid 90s and has worked in the retail side of the marine aquarium trade for more than ten years. He has a bachelor’s degree in Marine Science and has been the managing editor of ReefBuilders.com since 2008. Jake is interested in every facet of the marine aquarium hobby from the concepts to the technology, rare fish to exotic corals, and his interests are well documented through a very prolific career of speaking to reef clubs and marine aquarium events, and writing articles for aquarium publications across the globe. His primary interest is in corals which Jake pursues in the aquarium hobby as well as diving the coral reefs of the world.